Federal auto-safety regulators are opening an investigation into nearly one million General Motors pickup trucks and sport-utility vehicles after receiving hundreds of reports of engine failures.

The National Highway Traffic Safety Administration said Friday it was launching the probe into vehicles equipped with a particular GM V-8 engine that had already been the subject of an earlier recall. The regulator has received nearly 500 complaints alleging engine failure in vehicles that had already been serviced under recall, including nearly two dozen that required complete engine replacements.

The regulator's newest probe covers nearly 998,000 vehicles, including model years 2021 to 2026 of the Cadillac Escalade and Chevrolet Silverado, two of GM's most profitable models.

"The safety and satisfaction of our customers are the highest priorities for the entire GM team, and we continue to cooperate with NHTSA's evaluation of this matter," a GM spokesman said.

The probe marks the latest setback GM has faced in dealing with costly safety issues stemming from this V-8 engine, known internally as the L87. The automaker issued a recall last year for nearly 600,000 vehicles from the 2021 to 2024 model years to address concerns related to L87 engine failure, which GM attributed to a supplier. GM said it would either provide owners with a higher-viscosity oil or replace the engine entirely.

At the time, executives said the engine had resulted in around $500 million of incremental expenses as a result of the problem, according to an earnings-call transcript.

In January, NHTSA said it had concerns about the adequacy of the recall, following three dozen complaints from owners alleging engine failure had occurred even after receiving GM's fix.

Paul Jacobson, GM's chief financial officer, told analysts later that month that the company didn't believe any additional vehicles would need to be recalled going forward.

On Friday, NHTSA said it has also received an additional 191 reports of engine failure in vehicles produced after the production period covered by the earlier recall. The regulator also received a report of one crash and injury.

NHTSA said it would continue to investigate complaints of engine failure in vehicles that received the original defect fix and expand its probe to cover engines in newer pickups and SUVs with the L87.